Sulfur Amino Acids in Diet-induced Fatty Liver: A New Perspective Based on Recent Findings

Abstract

Abstract:The relationship of sulfur amino acids to diet-induced fatty liver was established 80 years ago, with cystine promoting the condition and methionine preventing it. This relationship has renewed importance today because diet-induced fatty liver is relevant to the current epidemics of obesity, non-alcoholic fatty liver disease, metabolic syndrome, and type 2 diabetes. Two recent papers provide the first evidence linking sulfane sulfur to diet-induced fatty liver opening a new perspective on the problem. This review summarizes the early data on sulfur amino acids in fatty liver and correlates that data with current knowledge of sulfur metabolism. Evidence is reviewed showing that the lipotropic effect of methionine may be mediated by sulfane sulfur and that the hepatosteatogenic effect of cystine may be related to the removal of sulfane sulfur by cysteine catabolites. Possible preventive and therapeutic strategies are discussed.

Concentrations of lead and other elements in the liver of the white-tailed eagle (Haliaeetus albicilla), a European flagship species, wintering in Eastern Poland

“…To cope with this vital sulfur requirement, sulfur metabolism is normally directed to the intake of methionine and cysteine for protein synthesis, but neither cysteine nor methionine is stored in the body. Any dietary excess is readily oxidized to sulfate, excreted in the urine (or reabsorbed depending on dietary levels) or stored in the form of glutathione (Nimni et al 2007 ), and these processes are related to the supply of sulfur, which is collected in the form of amino acids, to a healthy body (Nimni et al 2007 , Netto et al 2014 , Toohey 2014 ). The birds examined in this study accumulated 40–50% less S in their livers (Table 6 ) than eagles from Western Poland (Falandysz et al 2001 ) (mean: 17 000 mg kg −1 dw), which may indicate (in the context of very high levels of hepatic Pb) problems in the supply of sulfur necessary for detoxification.…”

“…Research indicates that proteins rich in sulfur amino acids play an important role in detoxification. Detoxification processes are determined by the proper intake of sulfur (in the form of sulfur amino acids) (Tamas and Martinoia 2006 ; Nimni et al 2007 ; Toohey 2014 ).…”

Trace element concentrations in livers of Common Buzzards Buteo buteo from eastern Poland

“…Neither age ( F 1,30 = 0.005, p = 0.95) nor sex ( F 1,30 = 1.10, p = 0.30) significantly affected the concentration of S. A difference in the intensity of the elimination of toxic elements among the individuals probably explained the differences in hepatic concentrations of S between immature females and males (Table 3 ). Hg, Cd, and Pb detoxification processes may be associated with high S demand because of sulfur amino acid involvement (Quig 1998 , Miles et al 2000 , Tamas and Martinoia 2006 , Netto et al 2014 , Toohey 2014 ). Hepatic concentrations of S are rarely studied in birds.…”

90th Anniversary Commentary: Amino Acid Imbalances: Still in the Balance

“…This pellagragenic effect of leucine is attributed to an increased hepatic oxidation of tryptophan (36). The phenomenon of diet-induced fatty liver is also linked to an imbalanced intake of sulfur-containing amino acids (37), occurring with both low and high intakes. It is also relevant today in aid-based human nutrition, where diets in many poorer parts of the world are heavily cereal-based and present the risk of being deficient in lysine (38).…”